Transcript Vex Robotics

Vex Robotics
Program four: reversing and
turning
Program four: reversing and turning
In this section, you will enhance the
code from program three by making it
back up, turn, and then continue on its
way when the bumper sensor is hit,
rather than just stopping.
Open your saved
program three file.
Select “Open
Project” from the
“File” menu, then
click on INTRO
PROGRAM THREE
and click “Open”.
Before editing the
code, save the
code as “intro
program four”.
 The current programmed behavior is:
 if the bump sensor is not being pressed in, the motors turn
on;
 when the bump sensor is pressed in, the motors turn off.
 We will edit this program so that instead of stopping
when the bump sensor is pushed, your robot will
back up, turn right, and then resume moving
forward.
 This means that the new turn-backup code will be
replacing the old stop code icons in the else
statement.
 Start by clearing away the old code.
 Delete both of the Motor Module commands in the
else statement.
 Right-click the first icon, then select delete from the
menu that appears.
 A screen will appear asking if you are sure;
 Next, we want to start building the new
behavior into the else statement.
 Begin with the first action, backing up (the
idea is to move your robot clear of the
obstacle it has encountered).
 To do this, drag in two “Motor module” icons
between the brackets of the else statement.
 Configure them so the robot starts moving in
reverse.
 Set the amount of time for
the robot to move with a
“Wait” icon like you did in
program two (page #).
 Drag a “Wait” icon into
the else statement under
the two “Motor Module”
icons. In the “Wait”
configuration window, set
the “Wait [msec]” to 1000
(one second.)
To make your robot
turn right, drag two
“Motor Module”
icons below the
wait icon, inside
the else statement.
Configure them so
the robot turns
right.
 To specify the amount of time your robot will
turn right, drag a “Wait” icon into the else
statement under the two “Motor Module”
icons.
 In the “Wait” configuration window, set the
“Wait [msec]” to 500 (which is 500ms, or half
a second.)
 This should make your robot turn
approximately ninety degrees.
 Note: The amount of turning produced by
this program will vary from robot to robot.
 You may have to tweak the timing for your
robot to turn away from the wall.
Compile and Download your program.
Refer to the programming sequence
section for detailed steps on compiling
and downloading.
Test your code.
Your robot should drive forward until
the front bump sensor is hit, at which
point the robot will back up, turn right,
and then resume forward motion.
Be sure to save changes to your code.
Congratulations! Your robot now performs
an intelligent autonomous behavior!
Let your robot run for a while to see how
long it can continue roaming around a
room.
Identify areas for improvement in the
design, and construct and program an
improved version.